Question

我是Android的新手，并且一直在使用一个简单的库存应用程序并且已经遇到了这个问题：

在我的“设置库存”屏幕上，产品列表和当前库存从数据库中获取并显示在以编程方式生成的2列TextView中。

onCreate方法，它从数据库中获取并将其放入activity_set.xml中的空ListView中：

public class SetActivity extends AppCompatActivity{
    private static final String TAG = "SetActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_set);

        ArrayList<Product> stock = Products.retrieveProducts(this);
        final ListView mListView = (ListView) findViewById(setList);
        ProductEditAdapter adapter = new ProductEditAdapter(this,R.layout.adapter_set_layout, stock);
        mListView.setAdapter(adapter);

    }

ProductEditAdapter类：

public class ProductEditAdapter extends ArrayAdapter<Product> {
    private static final String TAG = "ProductEditAdapter";
    private Context mContext;
    int mResource;


    public ProductEditAdapter(Context context, int resource, ArrayList<Product> objects){
        super(context,resource,objects);
        mContext = context;
        mResource = resource;

    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        String name = getItem(position).getName();
        int stock = getItem(position).getStock();
        Product product = new Product(name,stock);
        LayoutInflater inflater = LayoutInflater.from(mContext);
        convertView = inflater.inflate(mResource, parent, false);
        TextView tvName = (TextView) convertView.findViewById(R.id.pie_name);
        TextView tvCurrentStock = (TextView) convertView.findViewById(R.id.current_stock);
        tvCurrentStock.setText(String.valueOf(stock));
        tvName.setText(name + ":");
        tvCurrentStock.setTag(name);
        return convertView;
    }
}

使用以下命令创建adapter_set_layout.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/adapsetLayout"
    android:weightSum="100">

    <TextView
        android:gravity="center"
        android:textAlignment="center"
        android:text="TextView1"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:id="@+id/pie_name"
        android:layout_weight="20"
        android:textColor="#000000"
        android:textStyle="bold"
   />

    <TextView
        android:gravity="center"
        android:textAlignment="center"
        android:text="TextView1"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:id="@+id/current_stock"
        android:layout_weight="80"
        android:textColor="#000000"
        android:textStyle="bold"
        android:onClick="onClick"
        android:clickable="true"
        />
</LinearLayout>

当您点击某个项目的库存时，您会弹出一个新的数字，然后您可以单击“确定”以更新该TextView，或单击“取消”。

然后有一个提交按钮，它解析所有TextView并将数据库中每个产品的库存号更新为新值。

更改的TextView值在临时提交之前是暂时的，如果您离开屏幕，它将恢复为从中获取的值。

SetActivity中的onClick方法：

public void onClick(View v){
    if(v.getId()==R.id.submitButton) {
      confirmDialog();
    }
    else if(v.getId()==R.id.current_stock) {
        LinearLayout parent = (LinearLayout) v.getParent();
        final TextView pie_stock_view = (TextView) parent.findViewById(current_stock);
        final TextView pie_name_view = (TextView) parent.findViewById(pie_name);


        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle(pie_name_view.getText().toString());

        final EditText input = new EditText(this);
        input.setInputType(InputType.TYPE_CLASS_NUMBER);
        builder.setView(input);

        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                pie_stock_view.setText(input.getText().toString());
            }
        });
        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });

        builder.show();


    }
    else if(v.getId()==R.id.resetButton) {
        resetDialog();
    }

}

该应用程序在模拟器中运行良好 - 当您单击一个库存号并弹出该框时，您只需键入桌面键盘并单击确定，在提交之前更新任意数量的值。

实际设备上的问题是当弹出框并点击它时，屏幕上的键盘会弹出，我猜这会被视为离开活动，因为所有更新的值都是重置回他们生成的值，任何建议如何防止这种情况？。

Answer 1

您应该将更改后的值存储在数组中。为了首先使用另一个函数来捕获点击并将stock数组的定义移到onCreate之外。因此，您可以将代码更改为：

public class SetActivity extends AppCompatActivity{
    private static final String TAG = "SetActivity";
    ArrayList<Product> stock = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_set);
        if(stock == null)
            stock = Products.retrieveProducts(this);
        final ListView mListView = (ListView) findViewById(setList);
        ProductEditAdapter adapter = new ProductEditAdapter(this,R.layout.adapter_set_layout, stock);
        mListView.setAdapter(adapter);


        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            public void onItemClick(AdapterView parent, View v, int position, long id){
                if(v.getId()==R.id.submitButton) {
                    confirmDialog();
                }
                else if(v.getId()==R.id.current_stock) {
                    LinearLayout parent = (LinearLayout) v.getParent();
                    final TextView pie_stock_view = (TextView) parent.findViewById(current_stock);
                    final TextView pie_name_view = (TextView) parent.findViewById(pie_name);


                    AlertDialog.Builder builder = new AlertDialog.Builder(this);
                    builder.setTitle(pie_name_view.getText().toString());

                    final EditText input = new EditText(this);
                    input.setInputType(InputType.TYPE_CLASS_NUMBER);
                    builder.setView(input);

                    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                        pie_stock_view.setText(input.getText().toString());
                        getItem(position).setStock(input.getText().toString());
                        }
                    });
                    builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                        }
                    });

                    builder.show();

                }
                else if(v.getId()==R.id.resetButton) {
                    resetDialog();
                }

            }
        });
    }
}

另一个重要的事情是尝试使用convertView。它可以防止内存泄漏并提高应用程序的性能。

 @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        String name = getItem(position).getName();
        int stock = getItem(position).getStock();
        Product product = new Product(name,stock);
        if(convertView != null){
            LayoutInflater inflater = LayoutInflater.from(mContext);
            convertView = inflater.inflate(mResource, parent, false);
        }
        TextView tvName = (TextView) convertView.findViewById(R.id.pie_name);
        TextView tvCurrentStock = (TextView) convertView.findViewById(R.id.current_stock);
        tvCurrentStock.setText(String.valueOf(stock));
        tvName.setText(name + ":");
        tvCurrentStock.setTag(name);
        return convertView;
    }

键盘打开时Android TextViews清除？

1 个答案: